Recombinant chimeric acetylcholine receptors and their derivatives recognized by cd4 t cells of myasthenic patients for the treatment of myasthenia gravis

ABSTRACT

The present invention relates to recombinant acetylcholine receptor polypeptides recognized by CD4 T cells of a myasthenia gravis patient and compositions for the treatment of myasthenia gravis containing the same as an effective ingredient, more precisely, recombinant acetylcholine receptor polypeptides deficient in B cell epitope, recombinant acetylcholine polypeptides in which two or more T cell epitopes are fused, a composition for the treatment of myasthenia gravis containing the above recombinant polypeptides as an effective ingredient and a treatment method for myasthenia gravis using the composition. The composition containing one or more recombinant polypeptides above can be effectively used as a myasthenia gravis specific therapeutic agent or immunomodulator without side effects.

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention relates to recombinant chimeric acetylcholine receptor polypeptides recognized by CD4 T cells of a myasthenia gravis patient and chimeric acetylcholine derivatives for the treatment of myasthenia gravis containing the same as an effective ingredient, more precisely, recombinant acetylcholine receptor polypeptides deficient in B cell epitopes, recombinant acetylcholine polypeptides in which two or more T cell epitopes are fused, a composition for the treatment of myasthenia gravis containing the above recombinant polypeptides as an effective ingredient and a treatment method for myasthenia gravis using the compositions.

(b) Description of the Related Art

Autoimmune disease is led by the immune response induced against self-components (proteins or cells) according to the loss of self-tolerance. T cells regulating immune response are matured in thymus, in which they are instructed to cause immune response by recognizing an antigen linked to their MHC (major histocompatibility complex). Basically, T cells can not respond to those cells that have their own antigens in their MHC, but from time to time, self-active T cells are generated to recognize an antigen complex produced by the combination of their MHC and the antigens therein. Autoimmune disease is not infectious but inherited. In some cases, autoimmune disease can be triggered or worsened by virus infection, aging, chromium poisoning, hormones and pregnancy.

Autoimmune disease is a chronic disease, whose cause has not been disclosed, yet. Studies on autoantigens have been underway. Most autoimmune diseases are closely related to the activities of T cells, B cells and antigen presenting cells. Approaches to treat such autoimmune diseases are largely outlined by following four methods; first, targeting a subject which is involved in the activity of an immune cell; second, regulating an antigen-specific immune response; third, reconstructing immune system by transplanting autologous or allogeneic stem cells; and fourth, transplanting an organ. Besides, to treat autoimmune diseases, conventional immunosuppressants have been widely used, which are exemplified by calcineurin inhibitors (cyclosporin, tacrolimus), antimetabolites (azathioprine, leflunomide, methotrexate, mycophenolate mofetil), antiproliferatives (sirolimus), monoclonal antibodies to T lymphocyte (basiliximab, daclizumab, muromonab-CD3) and anticytokines (anakinra, etanercept, infliximab). Recently, approximately more than 23 immunosuppressants are under clinical trial or ready for the trial (Expert Opin Emerg Drugs. 2003 May; 8(1):47-62). The gene therapy has recently been tried out to treat autoimmune diseases, for example, CD4+ T cells are infected with a vector specially designed to express cytokines (IL-4, IL-10, IL-12p40) having functions of immunoregulation, which are then amplified to be used as a cell therapy agent (Autoimmun Rev. 2002; 1(4):213-9); Curr Opin Immunol. 2001; 13(6):676-82). However, the above methods not only inhibit abnormal autoimmune responses but also suppress normal immune response to protect human body from an invading antigen, so that it might increase the chances of infectious diseases and other side effects including weakening the function of inhibiting tumor expression by immune cells.

Another attempt has been made to treat autoimmune disease. Oral administrations of autoimmune disease specific antigens have induced antigen-specific immune tolerance in various experimental autoimmune animal models. These are including following experimental autoimmune model systems; bovine/chicken collagen for the treatment of rheumatoid arthritis, myelin basic protein for the treatment of multiple sclerosis, insulin for the treatment of type-I diabetes and IRBP (interphotoreceptor retinoid-binding protein) for the treatment of autoimmune uveitis. However, the oral administration of these antigens was effective mainly in animal models but not in human clinical trials. There are still problems in the development of an oral immune regulator. The immune responses mediated by CD8 cells and B cells against orally administered proteins have not been considered.

In summary, for the development of safe and effective oral immunomodulator potential immunoactivator function of orally administered protein should be considered. For example, to develop oral immunomodulator targeting CD4 T cell immune responses, orally administered proteins should induce hypoimmune response to administered antigen-specific CD4+ T cells without stimulating immune responses mediated by antigen-specific B cells and CD8 cells.

Myasthenia gravis is one of chronic autoimmune diseases, which has the incidence of 1/5,000-10,000. Currently antigen-specific therapeutic agent for myasthenia gravis has not been developed, yet. Myasthenia gravis is developed when the normal binding acetylcholine to acetylcholine receptor (referred as “AChR” hereinafter) is interrupted in neuromuscular junction. In Myasthenia gravis anti-AChR antibody to self-AChR acts as an inhibitor of signal transduction in the neuromuscular junction. In fact, approximately 80% of myasthenia gravis patients have been reported to harbor antibodies responding to AChR. The antibody responding to AChR can be a direct cause of the disease and the generation of the antibody is essentially involved in the action of T cells. Namely generation of AChR-specific antibody is depending on AChR-reactive T cell. Therefore, any substance that can incapacitate AChR-specific T cells or B cells can be used for the treatment of myasthenia gravis. For the treatment of myasthenia gravis, non-specific treatment methods (immune inhibitor, intravenously injectable immunoglobulin, and plasmapheresis) and acetylcholine esterase inhibitor known as mestinon are in use, and the market for them is growing every year. Nevertheless, the therapeutic agents in use have side effects and show limited effects.

AChR is composed of two α, β, γ and δ (ε) chains. Most autoimmune response related T cell and B cell antigens localize in the α chain (see FIG. 1), particularly in the extracellular domain of the α chain, and B cell epitope known as MIR (main immunogenic region) and various AChR-reactive epitopes antigens are also localized in non-alpha chains.

US Patent Publication No. 2002-0081652 describes the production of a polypeptide derived from human AChR α subunit. But, the polypeptide still harbors the B cell epitopes that could be recognized by auto-AChR reactive B-cell receptors in myasthenia gravis. This could be harmful when B-cell epitope-containing human AChR α subunit is administered into a myasthenia gravis patient or animal since AChR-reactive B-cell receptors could recognizes B cells, thereof to activate AChR-reactive B cells as well as T cells. Indeed when B-cell epitope containing human AChR α subunit was administered in acute state of myathenic rats it exacerbated myasthenia by stimulating AChR-reactive T cells as well as B cells (Im et al., J Immunol., 165: 3599-3605, 2000).

The present inventors produced a polypeptide by inserting P3A sequence which is composed of 25 amino acids expressed only in some of acetylcholine receptors into the region between the 58^(th) and the 59^(th) amino acids among 1^(st)-205^(th) amino acids of human AChR α subunit, and then confirmed that the produced polypeptide characteristically has the structure reducing antigenicity of B cell epitope against myasthenia gravis. The present inventors further induced immune tolerance against an autoantigen by the oral administration of the produced polypeptide to an animal model with myasthenia gravis (Im et al., J Clin. invest., 165:3599-3605, 2000). And also, the present inventors made an attempt to treat myasthenia gravis by the intranasal administration of the produced polypeptide to an animal model with myasthenia gravis (Im et al., J Neuroimmunol., 111(1-2) :161-168, 2000).

SUMMARY OF THE INVENTION

It is an object of the present invention to provide recombinant polypeptides of acetylcholine receptor (referred as “AChR” hereinafter) deficient in B cell epitopes, the genes thereof and polynucleotides encoding the same.

It is another object of the present invention to provide an expression vector containing a polynucleotide encoding the above polypeptide and a transformant transformed with the vector.

It is another object of the present invention to provide recombinant chimeric AChR polypeptides in which two or more T cell epitopes are linked and a gene thereof and polynucleotides encoding the same.

It is another object of the present invention to provide an expression vector harboring polynucleotides encoding the above polypeptide and an E. coli transformants transfected with the vector.

It is another object of the present invention to provide a therapeutic agent for myasthenia gravis containing AChR recombinant polypeptide in which B cell epitopes are deleted and/or AChR recombinant polypeptides in which T cell epitopes of myathenic patients are linked.

It is a further object of the present invention to provide a method for the treatment of myasthenia gravis containing the step of administrating the effective dose of AChR recombinant polypeptide in which B cell epitope is deleted and AChR recombinant polypeptide in which T cell epitopes are fused to a mammalian.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing the structure of α subunit of human acetylcholine receptor (referred as “hAChR” hereinafter).

FIG. 2 is a diagram illustrating the sequence deficiency between 67_(th)-76^(th) and 129^(th)-145^(th) amino acid of hAChR α subunit:

FIG. 2 a is deficiency in amino acid sequence between 67^(th)-76^(th), 129^(th)-145^(th), confirmed by electrophoresis:

A: deficiency in amino acid sequence between 67^(th) and 76^(th), confirmed by electrophoresis;

-   -   M: marker;     -   1: pThioHis-Ha1-210;     -   2: pThioHis-Ha1-210Δ67-76;

B: deficiency in amino acid sequence between 129^(th) and 145^(th), confirmed by electrophoresis;

-   -   M: marker;     -   1: pThioHis-Ha1-210Δ67-76;     -   2: pThioHis-Ha1-210Δ67-76Δ129-145;

FIG. 2 b is diagram illustrating the sequence deficiency between 67^(th)-76^(th) and 129^(th)-145^(th) amino acid of hAChR α subunit:

C: plasmid map of pThioHis-Ha1-210; and

D: deficiency in amino acid sequence between 67^(th) 76^(th) and 129^(th)-145^(th).

FIG. 3 is a diagram showing the comparison of nucleotide sequences between hAChR α subunit and the deletion form of hAChR α subunit:

A: deficiency in amino acid sequence between 67^(th) and 76^(th) amino acid of B cell epitope;

B: deficiency in amino acid sequence between 129^(th) and 145^(th) amino acid of B cell epitope; and

Straight line: sequence-corresponding region.

FIG. 4 is a diagram showing the comparison of amino acid sequences between hAChR α subunit and the deletion form of hAChR α subunit:

Straight line: the location of a deleted primer; and

Square box: the location where B cell epitope is deleted.

FIG. 5 is an electrophoresis photograph illustrating the expression of hAChR α subunit, B cell epitope deleted polypeptide in E. coli:

A: SDS-PAGE;

B: western blot using a monoclonal antibody (mAB 198) having an affinity for hAChR α subunit MIR (maim immunogenic region);

1: Trx-Ha1-210 Δ67-76 Δ129-145;

2: Trx-Ha1-210; and

M: marker.

FIG. 6 is a graph illustrating the weight changes in an animal model according to the oral administration of the polypeptide composition with the deletion of B cell epitope of the hAChR α subunit:

TrxHa1-210: hAChR 1-210; and

TrxHa1-210ΔΔ: B cell epitope is deleted between 67^(th)-76^(th) and 129^(th)-145^(th) in hAChR 1-210.

FIG. 7 is a graph illustrating clinical scores obtained after the oral administration of the polypeptide composition with the deletion of B cell epitope of the hAChR α subunit to an animal model:

TrxHa1-210: hAChR 1-210; and

TrxHa1-210ΔΔ: B cell epitope is deleted between 67^(th)-76^(th) and 129^(th)-145^(th) in hAChR 1-210.

FIG. 8 is a diagram showing the structures of CD4+ cell epitopes of hAChR β, γ and ε subunits and oligomers thereof.

FIG. 9 is a schematic diagram illustrating the cloning of CD4+ T cell epitopes of hAChR β, γ and δ subunit genes.

FIG. 10 is an electrophoresis photograph illustrating the formation of a plasmid containing part A and part B composed of the combinations of T cell epitopes among hAChR β, γ and ε subunit chains.

FIG. 11 is a SDS-PAGE photograph illustrating the expression of E. coli strain transformed with an expression vector harboring hAChR CD4+ cell epitope:

M: marker;

1: IPTG untreated;

2: IPTG treated; and

Arrow: Trx:T cell epitope peptide.

FIG. 12 is a diagram showing CD4+ T lymphocyte epitope of hAChR subunit of a myasthenia gravis patient.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

To achieve the above objects, the present invention provides recombinant polypeptides of acetylcholine receptor (referred as “AChR” hereinafter) deficient in B cell epitope, the genes thereof and polynucleotides encoding the same.

The present invention also provides an expression vector containing a polynucleotide encoding the above polypeptide and a transformant transformed with the vector.

The present invention also provides an AChR recombinant polypeptide in which two or more T cell epitopes are fused and a gene thereof and a polynucleotide encoding the same.

The present invention also provides an expression vector harboring a polynucleotide encoding the above polypeptide and an E. coli transformant transfected with the vector.

The present invention also provides a therapeutic agent for myasthenia gravis containing AChR recombinant polypeptide in which B cell epitope is deleted and/or AChR recombinant polypeptide in which T cell epitopes are fused.

The present invention further provides a method for the treatment of myasthenia gravis containing the step of administrating the effective dose of AChR recombinant polypeptide in which B cell epitope is deleted and AChR recombinant polypeptide in which T cell epitopes are fused to a mammalian.

Hereinafter, the present invention is described in detail.

The present invention provides recombinant polypeptides of human acetylcholine receptor (referred as “hAChR” hereinafter) deficient in B cell epitope. The hAChR is composed of two α, β, γ and δ (ε) chains. However, most B lymphocyte antigens involved in autoimmune responses localize in the α chain, particularly the extracellular domain of the α chain. Therefore, the hAChR fragment is deficient in B cell epitope in amino acid sequence corresponding to the extracellular domain of the α chain, which is preferably represented by SEQ. ID. NO: 32, NO: 33 or NO: 34 and more preferably is represented by SEQ. ID. NO: 34.

In the present invention, a recombinant hAChR polypeptide lacking B cell epitope was amplified by polymerase chain reaction (referred as “PCR” hereinafter) using hAChR gene derived from cDNA of mRNA of TE671 cell line as a template and a set of primers represented by SEQ. ID. NO: 1 and NO: 2. The PCR product was inserted into pThio-HisA vector (Invitrogen, USA), which was then named pThio-HisHa1-210. To delete 67^(th)-76^(th) and 129^(th) -145^(th) amino acids, on which B cell epitope resides, PCR was performed again to prepare a deletion form by using pThio-HisHa1-210 as a template with the deletion primer 1 represented by SEQ. ID. NO: 3 and NO: 4 and the deletion primer 2 represented by SEQ. ID. NO: 5 and NO: 6 (see FIG. 2). The prepared polypeptide was orally administered together with hAChR α subunit polypeptide to a myasthenia gravis animal model and the weight changes of the animal were observed, followed by clinical scoring. The administration of B cell epitope deleted hAChR α subunit polypeptide relieved weight-loss, compared with hAChR α subunit polypeptide (see FIG. 6). From the results of clinical scoring, hAChR polypeptide showed worse clinical scores than B cell epitope deleted hAChR polypeptide (see FIG. 7).

The present invention also provides a polynucleotide encoding the polypeptide of the invention. There are various codons which are encoding the same amino acid owing to codon degeneracy. So, even if genes are encoding the same amino acid, they might have different nucleotide sequences. And the gene of the invention is preferably represented by SEQ. ID. NO: 35, NO: 36 or NO: 37.

The present invention further provides an expression vector harboring the polynucleotide and a transformant prepared by inserting the expression vector into a host cell. The biochemically active polypeptide or the fragment thereof can be separated or produced by cloning the polynucleotide which also enables the expression of a target gene in an appropriate host cell. To do so, a DNA molecule (polynucleotide) is inserted into a plasmid or a virus vector for the efficient self-replication in a selected host cell. The expression vector thereby can be used for the transformation of such host cells as eukaryotes and prokaryotes. The expression vector available for the transformation of prokaryotes is exemplified by a plasmid such as pThio-HisA (Invitrogen, USA) which is reproductive in E. coli and a bacteriophage vector such as λgt11, λgt18-23 and M13 originated vector, but not always limited thereto. The expression vector for the transformation of eukaryotes is exemplified by retrovirus and vaccinia virus, but not always limited thereto, either. To transform a host cell with the expression vector containing the nucleotide of the invention, one of the following methods which are well-known to those in the art can be selected; transformation, transfection, lipofection, conjugation, protoplast fusion, electroporation, calcium phosphate precipitation and direct microinjection. It is preferred to select a host cell from a group consisting of E. coli, a yeast such as Saccharomyces cerevisiae, an insect cell line such as Sf9 (Spodoptera frugiperda) and a mammalian cell line such as CHO (Chinese hamster ovary), but not always limited thereto. Prokaryotic cells are appropriated host cells for the production of the polypeptide of the invention. Since a non-native polypeptide has been proved to be more successful than a native polypeptide, it is expected that the polypeptide expressed in a prokaryotic system will be more successful than that in an eukaryotic system.

The present invention also provides a recombinant polypeptide with the fusion of two or more T cell epitopes of AChR. The present inventors tried to induce immune tolerance by using the T cell epitope fused recombinant polypeptide. Cytoplasmic site of AChR is normally in the inside of a cell so that it can be protected from any antibody response. But, as a disease progresses, cell membrane can be destroyed by the reaction of antibody and complements, and thus immune response can reach the inside of a cell through cell membrane. Thus, in the present invention, T cell epitope includes not only the one in α chain but also T cell epitopes in cytoplasmic site and amino terminal region. It is preferred to select the T cell epitope from a group consisting of the epitope having an amino acid sequence represented by SEQ. ID. NO: 38 (α 48-67); the epitope having an amino acid sequence represented by SEQ. ID. NO: 39 (α 101-120); the epitope having an amino acid sequence represented by SEQ. ID. NO: 40 (α 118-137); the epitope having an amino acid sequence represented by SEQ. ID. NO: 41 (α 304-328); the epitope having an amino acid sequence represented by SEQ. ID. NO: 42 (α 403-421); the epitope having an amino acid sequence represented by SEQ. ID. NO: 43 (α 419-437); the epitope having an amino acid sequence represented by SEQ. ID. NO: 44 (β 181-210); the epitope having an amino acid sequence represented by SEQ. ID. NO: 45 (β 271-290); the epitope having an amino acid sequence represented by SEQ. ID. NO: 46 (β 316-350); the epitope having an amino acid sequence represented by SEQ. ID. NO: 47 (γ 75-94); the epitope having an amino acid sequence represented by SEQ. ID. NO: 48 (γ 321-340); the epitope having an amino acid sequence represented by SEQ. ID. NO: 49 (ε 91-110); and the epitope having an amino acid sequence represented by SEQ. ID. NO: 50 (ε 141-160). Any recombinant polypeptide with the fusion of two or more epitopes selected from the above can be included in the criteria of the present invention, but a polypeptide with the fusion of 7 different epitopes and having the amino acid sequence represented by SEQ. ID. NO: 51 is preferred. A polypeptide with the fusion of all the 13 epitopes and having the amino acid sequence represented by SEQ. ID. NO: 53 is more preferred. At this time, the arrangement or the order of those T cell epitopes does not matter for the fusion.

To provide a polypeptide with the fusion of T cell epitopes of hAChR β, γ and ε chains, the present inventors designed an active site responding to CD4+ T cells to be composed of part A comprising 13 oligomers represented by SEQ. ID. NO: 7-NO: 19 and part B comprising 12 oligomers represented by SEQ. ID. NO: 20-NO: 31, based on the CD4+ T cell active site for each subunit of human acetylcholine of a myasthenia gravis patient. The single-stranded oligomer of part A or part B was synthesized by using Pfu, which was inserted into pGEM-T vector and named as pGEM-T easy Part A and pGEM-T easy Part B, respectively. Then, part A and part B were inserted together into pThio-HisA vector by using a restriction enzyme, which was named pThio-HisA-PartA-PartB. E. coli strain Top10 was transformed with the pThio-HisA-PartA-PartB, followed by confirmation of the transformation by SDS-PAGE (see FIG. 11).

The present invention provides a polynucleotide encoding the polypeptide of the invention, and the polynucleotide is preferably represented by SEQ. ID. NO: 52 or NO: 54. The present invention also provides an expression vector with the insertion of the polynucleotide and a transformant produced by inserting the expression vector to a host cell. The biochemically active polypeptide or the fragment thereof can be separated or produced by cloning the polynucleotide which also enables the expression of a target gene in an appropriate host cell. To do so, a DNA molecule (polynucleotide) is inserted into a plasmid or a virus vector for the efficient self-replication in a selected host cell. The expression vector thereby can be used for the transformation of such host cells as eukaryotes and prokaryotes. The expression vector available for the transformation of prokaryotes is exemplified by a plasmid such as pThio-HisA (Invitrogen, USA) which is reproductive in E. coli and a bacteriophage vector such as λgt11, λgt18-23 and M13 originated vector, but not always limited thereto. The expression vector for the transformation of eukaryotes is exemplified by retrovirus and vaccinia virus, but not always limited thereto, either. To transform a host cell with the expression vector containing the nucleotide of the invention, one of the following methods which are well-known to those in the art can be selected; transformation, transfection, lipofection, conjugation, protoplast fusion, electroporation, calcium phosphate precipitation and direct microinjection. It is preferred to select a host cell from groups consisting of E. coli, a yeast such as Saccharomyces cerevisiae, an insect cell line such as Sf9 (Spodoptera frugiperda) and a mammalian cell line such as CHO (Chinese hamster ovary), but not always limited thereto. Prokaryotic cells are appropriated host cells for the production of the polypeptide of the invention. Since a non-native polypeptide has been proved to be more successful than a native polypeptide, it is expected that the polypeptide expressed in a prokaryotic system will be more successful than that in an eukaryotic system.

The present invention provides a therapeutic agent for myasthenia gravis containing a recombinant polypeptide of hAChR fragment lacking myasthenia gravis specific recombinant B cell epitope and/or a recombinant polypeptide with the fusion of two or more T cell epitopes of hAChR as an effective ingredient.

The therapeutic agent of the invention can additionally include a modified polypeptide represented by SEQ. ID. NO: 55.

A therapeutic composition of the invention includes the above effective ingredient by 0.0001-50 weight % for the total weight.

The therapeutic composition of the present invention can also include, in addition to the above-mentioned effective ingredients, one or more pharmaceutically acceptable carriers for the administration. Pharmaceutically acceptable carrier can be selected or be prepared by mixing more than one ingredients selected from a group consisting of saline, sterilized water, Ringer's solution, buffered saline, dextrose solution, maltodextrose solution, glycerol and ethanol. Other general additives such as anti-oxidative agent, buffer solution, bacteriostatic agent, etc, can be added. In order to prepare injectable solutions, pills, capsules, granules or tablets, diluents, dispersing agents, surfactants, binders and lubricants can be additionally added. The composition of the present invention can further be prepared in suitable forms for each disease or according to ingredients by following the method represented in Remington's Pharmaceutical Science (the newest edition), Mack Publishing Company, Easton Pa.

The therapeutic composition of the present invention can be administered orally or parenterally (for example, intravenous, hypodermic, local or peritoneal injection). The effective dosage of the composition can be determined according to weight, age, gender, health condition, diet, administration frequency, administration method, excretion and severity of a disease. The dosage of the composition is 0.3˜30 mg/kg per day, and preferably 0.5˜10 mg/kg per day. Administration frequency is once a day or preferably a few times a day.

The therapeutic composition of the present invention can be administered singly or treated along with surgical operation, hormone therapy, chemotherapy and biological reaction regulator, to prevent and treat myasthenia gravis.

The present invention provides a method for the treatment of myasthenia gravis containing the step of administrating the effective dose of AChR recombinant polypeptide in which B cell epitope is deleted and AChR recombinant polypeptide in which T cell epitope is fused to a mammalian.

According to the conventional method, non-specific immunosuppressants such as steroid, azathioprine and cyclosporine are used for the treatment of myasthenia gravis. On the contrary, according to the method of the invention, myasthenia gravis specific immune cells are targeted, indicating that immune system is not weakened during the treatment of myasthenia gravis. The recombinant polypeptide of the invention is preferably selected from a group consisting of the polypeptide represented by SEQ. ID. NO: 32-NO: 34; the polypeptide represented by SEQ. ID. NO: 51 or NO: 53; and the polypeptide represented by SEQ. ID. NO: 55. And the therapeutic agent for myasthenia gravis is preferably administered through the nasal cavity or oral cavity.

Practical and presently preferred embodiments of the present invention are illustrative as shown in the following Examples.

However, it will be appreciated that those skilled in the art, on consideration of this disclosure, may make modifications and improvements within the spirit and scope of the present invention.

EXAMPLE 1

Synthesis of Recombinant Construct (pThio-His Hα1-210Δ67-76, Δ129-145) DNA with the Deletion of B Cell Epitopes of Human Acetylcholine Receptor (hAChR) α Subunit (Hα1-210)

Human acetylcholine receptor (hAChR) α subunit (Hα1-210) gene derived from TE671 cell line was amplified by polymerase chain reaction (PCR) using a primer set represented by SEQ. ID. NO: 1 and NO: 2. PCR was performed as follows; denaturation at 95° C. for 60 seconds, annealing at 60° C. for 60 seconds, polymerization at 72° C. for 60 seconds, 30 cycles from denaturation to polymerization. 50 μg of the amplified DNA fragment was digested with 10 unit of each restriction enzyme Kpa I and EcoR I for 3 hours at 37° C., and then 50 μg of pThio-HisA vector (Invitrogen, USA), 1 unit of ligase and ligation buffer were reacted together for 10 hours at 16° C., followed by insertion. The product was named “pThio-HisHa1-210”. 50 ng of pThio-HisAHa1-210 plasmid DNA containing the nucleotide sequence of hAChR α subunit, 20 pmol of deletion primer 1 represented by SEQ. ID. NO: 3 and NO: 4 and 2.5 unit of Pfu DNA polymerase (Bioneer, Korea) were mixed in 1 μl of dNTP, to which distilled water was added until the final volume was made as 50 μl, followed by reaction through 18 times of PCR cycles performed at 95° C. for 30 seconds, at 55° C. for 60 seconds and at 68° C. for 300 seconds. Then, 0.5 μl of restriction enzyme DPN I (NEB, USA) was added thereto, followed by further reaction for 10 hours at 37° C. The reactant was mixed with 20 pmol of deletion primer 2 represented by SEQ. ID. NO: 5 and NO: 6 and 2.5 unit of Pfu DNA polymerase (Bioneer, Korea) in 1 μl of dNTP, to which distilled water was added to make the total volume 50 μl. PCR was performed as follows; at 95° C. for 30 seconds, at 55° C. for 60 seconds, at 68° C. for 300 seconds (18 cycles). 0.5 μl of restriction enzyme KPN I (NEB, USA) was added thereto, followed by further reaction for 10 hours at 37° C.. 2 μl of the final reaction solution was reacted with E. coli DH5α for 30 seconds at 42° C., which stood at 4° C. for 10 minutes thereafter. The mixture was smeared on an ampicillin containing medium and transformed E. coli cells were selected. The selected cells were cultured at 37° C. and a target plasmid lacking B cell epitope was separated by using Plasmid SV mini kit (GENEALL, Korea), which was named “pThio-HisHα1-210Δ67-76Δ129-145” (FIG. 2). Sequencing of the DNA was performed, so that the nucleotide sequences before and after the deletion were compared (FIG. 3). In addition, the location of B cell epitope and the structure of the deleted polypeptide were also examined (FIG. 4). As a result, the human acetylcholine receptor α subunit amino acid sequence was identified as the one represented by SEQ. ID. NO: 34.

EXAMPLE 2

Synthesis of a Recombinant Polypeptide with the Deletion of B Cell Epitopes of hAChR α Subunit (Hα1-210) and Confirmation of the Deletion of B Cell Epitope

50 ng of pThio-HisAHa1-210Δ67-76Δ129-145 DNA prepared in Example 1 was reacted with 50 μl of E. coli Top 10 for 30 seconds at 42° C., which stood for 10 minutes thereafter. The reaction solution was placed in an ampicillin containing medium, followed by the selection of transformed E. coli cells. The selected E. coli cells were cultured in 5 ml LB medium for 10 hours at 37° C. and the culture solution was inoculated into 1 l LB medium, followed by further culture for 3 hours at 37° C. 1 mM of IPTG was added to the culture solution, followed by culture for four more hours. Centrifugation was performed with 10,000×g to separate E. coli cells from the culture solution. The isolated E. coli cells were washed twice with 50 mM Tris buffer and the cells were homogenized with a sonicator. The homogenized E. coli cells were diluted in 50 mM Tris buffer, followed by centrifugation at 10,000×g to remove the supernatant. Then, the precipitate was dissolved in 9 M urea solution, followed by centrifugation at 20,000×g for one hour. The supernatant was transferred onto the dialysis membrane, followed by dialysis with 50 mM Tris buffer 5 times every three hour. Centrifugation was performed at 20,000×g and as a result, a target polypeptide was obtained from the supernatant, which was named “TrxHa1-210Δ67-76Δ129-145”. The polypeptide was electrophoresed on 12% SDS PAGE gel with 80 V for 2 hours and then transferred onto a nitrocellulose membrane (Biored, USA), followed by western blotting. After the transfer, the nitrocellulose membrane was soaked in a PBS solution containing 5% skim milk at room temperature for one hour to block the polypeptide-not-transferred regions. Western blotting was performed by using a monoclonal antibody (mAb 198, produced by Dr. Socrates Tzartos, Greece) having an affinity for MIR (main immunogenic region, Ha1-210 67-76) of AChR α chain. The membrane was reacted in PBS buffer containing the monoclonal antibody (mAb 198) for 90 minutes, followed by washing with PBS three times. Then, the membrane was treated with anti-mouse IgG-HRP (Sigma, USA) containing PBS for 60 minutes, followed by washing with PBS three times. The membrane was then reacted with ECL kit (Amersham Biosciences, UK) for one minute and then exposed on X-ray film.

From the SDS-PAGE, it was confirmed that Trx-Ha1-210Δ67-76Δ129-145 with the deletion of B cell epitope showed lower protein expression than Trx-Ha1-210 (see FIG. 5A). Also, from the Western blot analysis using the monoclonal antibody (mAb 198) having an affinity for MIR (main immunogenic region 67-76) of hAChR α subunit, it was confirmed that Trx-Ha1-210Δ67-76Δ129-145 had the deletion of B cell epitope (FIG. 5B).

EXAMPLE 3

Examination of Weight Changes and Clinical Score after Oral Administration of Polypeptides TrxHa1-210, TrxHa1-210Δ67-76Δ129-145 in Experimental Autoimmune Myasthenia Gravis

45 μg of Torpedo californica AChR was mixed with CFA (Complete Freund Adjuvant), which was injected rear pads of a rat at 6-7 weeks to induce immunization. From one week after the immunization with Torpedo californica AChR, 600 μg of each TrxHa1-210 and TrxHa1-210Δ67-76Δ129-145 were orally administered to 6 and 5 rats, respectively, by using orogastric tube (Fisher, USA) two times per week. Weight changes were measured and clinical scoring was performed once a week. To determined clinical score, the scores measured by two different observers by using double blind method were averaged. Score 0 indicates no symptoms, score 1 indicates a faint fatigue and a weak grip of a rat, score 2 indicates a slight weight loss and gibbosity, score 3 indicates a severe weight loss and trembling and score 4 indicates death.

The results of the experiment are shown in the below table. TABLE 1 Weight changes after oral administration of hAChR α subunit lacking B cell epitope Week 0.8 1 2 3 4 5 TrxHa1-210 0.00 7.46 1.02 0.6 11.36 3.04 Standard 0.00 1.86 0.92 2.62 1.81 4.78 Deviation TrxHa1-210DD 0.00 6.88 3.55 8.75 18.75 21.45 Standard 0.00 3.24 2.12 5.88 4.13 4.76 Deviation

As confirmed in the above results, the oral administration of hAChR α subunit polypeptide lacking B cell epitope to an animal model with myasthenia gravis slows down the weight loss, which is a typical symptom carried by the administration of hAChR α subunit polypeptide (FIG. 6). TABLE 2 Clinical score determined after the oral administration of hAChR α subunit lacking B cell epitope Week 0.8 1 2 3 4 5 TrxHa1-210 0.00 0.50 0.90 0.90 0.70 2.20 Standard 0.00 0.22 0.19 0.29 0.12 0.49 Deviation TrxHa1-210DD 0.5 1 0.625 0.875 0.25 0.5 Standard 0.50 0.58 0.13 0.38 0.14 0.35 Deviation

As confirmed in the above results, the oral administration of hAChR α subunit polypeptide lacking B cell epitope to an animal model with myasthenia gravis resulted in not worse clinical score than that resulted from the oral administration of hAChR α subunit polypeptide (FIG. 7).

EXAMPLE 4

Preparation of a Polypeptide Composed of CD4 T Cell Epitopes of hAChR α, β, γ and ε Chains Reacting to Myasthenia Gravis Patient

Nucleotide sequence composing the active site reacting to CD4+ T cells was designed to be composed of two major parts; which are part A comprising 13 oligomers represented by SEQ. ID. NO: 7-NO: 19 and part B comprising 12 oligomers represented by SEQ. ID. NO: 20-NO: 31 (FIG. 8). To obtain a DNA to which CD4+ T cell active sites are serially linked, 13 and 12 single-stranded DNA oligomers, respectively for part A and part B, were ordered at Cosmogenetech (Korea) . 25 pmol of each oligomer was mixed with 2.5 unit of Pfu, 4 μl of dNTP and 45 μl of distilled water, followed by PCR at 94° C. for 30 seconds, at 52° C. for 30 seconds and at 72° C. for 120 seconds (24 cycles). 1 μ of the final reaction solution was reacted with 1 unit of ligase of pGEM-easy cloning kit (Promega, USA) and ligase buffer for 12 hours at 16° C. to produce plasmid pGEM-PartA and pGEM-PartB. 50 μg of these vectors were reacted with 10 unit of restriction enzyme Nco I at 37° C. for 6 hours to prepare DNA fragments, which were linked to pThio-HisA vector (Invitrogen, USA) using T4 ligase, resulting in the expression vector pThio-HisA-PartA-PartB (FIG. 9). Electrophoresis was performed to confirm the production of the plasmid vector (FIG. 10). The expression vector was used to prepare polypeptides in which CD4+ T cell active sites were fused by the same manner as described in Example 2 and the production of those polypeptides were confirmed by electrophoresis using 12% SDS-PAGE gel at 90 V for 2 hours (FIG. 11).

EXAMPLE 5

Synthesis of Recombinant Polypeptides with T Cell Epitopes in hAChR (Hα1-210) are Fused

50 ng of pThio-HisA-PartA-PartB DNA prepared in Example 4 was reacted with 50 μl of E. coli Top 10 for 30 seconds at 42° C., which stood for 10 minutes thereafter. The reaction solution was placed in an ampicillin containing medium, followed by the selection of transformed E. coli cells. The selected E. coli cells were cultured in 5 ml LB medium for 10 hours at 37° C. and the culture solution was inoculated into 1 l LB medium, followed by further culture for 3 hours at 37° C. 1 mM of IPTG was added to the culture solution, followed by culture for four more hours. Centrifugation was performed with 10,000×g to separate E. coli cells from the culture solution. The isolated E. coli cells were washed twice with 50 mM Tris buffer and the cells were homogenized with a sonicator. The homogenized E. coli cells were diluted in 50 mM Tris buffer, followed by centrifugation at 10,000×g to remove the supernatant. Then, the precipitate was dissolved in 9 M urea solution, followed by centrifugation at 20,000×g for one hour. The supernatant was transferred onto the dialysis membrane, followed by dialysis with 50 mM Tris buffer 5 times every three hour. Centrifugation was performed at 20,000×g and as a result, a target polypeptide was obtained from the supernatant, which was named “TrxPartA-PartB”. The polypeptide was electrophoresed on 12% SDS PAGE gel with 90 V for 2 hours and then transferred onto a nitrocellulose membrane (Biored, USA), followed by Western blotting. After the transfer, the nitrocellulose membrane was reacted in a PBS solution containing 5% skim milk at room temperature for one hour to block the polypeptide-not-transferred regions. Western blotting was performed by using a monoclonal antibody (mAb 198, produced by Dr. Socrates Tzartos, Greece) having an affinity for MIR (main immunogenic region) of hAChR. Particularly, the membrane was reacted in PBS buffer containing the monoclonal antibody mAbl98 for 90 minutes and then washed three times with PBS. The membrane was reacted again in PBS containing anti-mouse IgG-HRP (Sigma, USA) for 60 minutes and then washed three times with PBS. The membrane was then reacted with ECL kit (Amersham Biosciences, UK) for one minute and then exposed on X-ray film.

EXAMPLE 7-EXAMPLE 8

Investigation on Weight Changes and Clinical Scoring after Oral Administration of Recombinant Polypeptides Composed of all CD4 T Cell Epitopes of hAChR

Recombinant polypeptides with various combinations of T cell epitopes were prepared in Example 6-Example 10 by the same manner as described in Example 4 and Example 5. The combinations of T cell epitopes are shown in Table 3. TABLE 3 Polypeptides with the combinations of T cell epitopes Name Combination Example 4 β 181-200, β 271-290, β 316-350, γ 75-94, γ 321-340, ε 91-110, ε 141-160 Example 6 α 48-67, α 101-120, α 118-167, α 304-328, α 403-421, α 419-437, β 181-200, β 271-290, β 316-350, γ 75-94, γ 321-340, ε 91-110, ε 141-160 Example 7 β 181-200, β 271-290, β 316-350, γ 75-94, γ 321-340 Example 8 β 181-200, β 271-290, β 316-350, ε 91-110, ε 141-160 Example 9 α 48-67, α 101-120, α 118-167, α 304-328, α 403-421, α 419-437, β 181-200, β 271-290, β 316-350, γ 75-94, γ 321-340 Example 10 α 48-67, α 101-120, α 118-167, α 304-328, α 403-421, α 419-437, β 181-200, β 271-290, β 316-350, ε 91-110, ε 141-160

Weight changes were observed in mice administered orally with recombinant polypeptides with the combinations of T cell epitopes prepared as shown in 5 Table 3 by the same manner as described in Example 3, followed by clinical scoring. The results are shown in Table 4 and Table 5. TABLE 4 Weight changes after oral administration of recombinant polypeptides with the combinations of T cell epitopes Week 0.8 1 2 3 4 5 ThrHa1-210 0.00 7.46 1.02 0.6 11.36 3.04 Standard 0.00 8.05 9.61 12.92 15.74 21.51 Deviation Example 4 0.00 4.01 3.10 4.45 6.23 9.36 Standard 0.00 2.24 5.30 4.21 3.24 8.22 Deviation Example 6 0.00 1.86 0.92 2.62 1.81 4.78 Standard 0.00 6.5 8.3 10.2 13.9 19.2 Deviation Example 7 0.00 6.24 8.90 11.01 12.36 17.58 Standard 0.00 1.35 2.00 5.21 3.39 5.70 Deviation Example 8 0.00 8.57 10.90 9.84 11.85 15.21 Standard 0.00 3.89 4.05 3.00 2.29 5.98 Deviation Example 9 0.00 5.52 7.76 9.36 14.55 20.34 Standard 0.00 0.05 1.17 4.50 3.78 9.10 Deviation Example 10 0.00 9.95 13.78 16.88 18.21 20.11 Standard 0.00 4.64 7.10 4.64 3.96 5.99 Deviation

As confirmed from the above results, weight loss was alleviated in an animal model with myasthenia gravis by the oral administration of polypeptides with the combinations of T cell epitopes. TABLE 5 Clinical scores according after oral administration of recombinant polypeptides with the combinations of T cell epitopes Week 0.8 1 2 3 4 5 TrxHa1-210 0.00 0.50 0.90 0.90 0.70 2.20 Standard 0.00 0.22 0.19 0.29 0.12 0.49 Deviation Example 4 0.5 1 0.87 0.64 0.25 0.31 Standard 0.4 0.51 0.51 0.27 0.19 0.15 Deviation Example 6 0.65 0.98 0.71 0.47 0.29 0.30 Standard 0.10 0.21 0.19 0.26 0.14 0.12 Deviation Example 7 0.45 1 0.85 0.63 0.41 0.32 Standard 0.21 0.51 0.54 0.31 0.19 0.10 Deviation Example 8 0.30 1.2 0.95 0.69 0.48 0.62 Standard 0.10 0.30 0.19 0.47 0.29 0.17 Deviation Example 9 0.35 1 0.71 0.52 0.33 0.30 Standard 0.29 0.54 0.33 0.24 0.11 0.19 Deviation Example 10 0.87 0.99 0.62 0.44 0.39 0.32 Standard 0.41 0.12 0.26 0.21 0.17 0.15 Deviation

As shown in the above results, the worsening of the clinical score was relieved by the oral administration of recombinant polypeptides with the combinations of T cell epitopes to an animal model with myasthenia gravis.

INDUSTRIAL APPLICABILITY

As explained hereinbefore, polypeptides with the deletion of B cell epitope of hAChR α subunit or with the recombinant chimeric AChR composed of CD4 T cell epitopes relieve the symptoms of myasthenia gravis in animal models. Therefore, the composition containing the polypeptide above or two or more the polypeptides above can be effectively used as a therapeutic agent specifically working on myasthenia gravis and/or immunomodulator without side-effects. 

1. A recombinant polypeptide of acetylcholine receptor α subunit with the deletion of B cell epitope.
 2. The recombinant polypeptide according to claim 1, wherein the B cell epitope has an amino acid sequence comprising 67^(th) to 76^(th) and/or 129^(th) to 145^(th) amino acids of acetylcholine receptor α subunit.
 3. The recombinant polypeptide according to claim 1, wherein the polypeptide is selected from a group consisting of sequences represented by SEQ. ID. NO: 32-NO:
 34. 4. A polynucleotide encoding the polypeptide of claim
 1. 5. The polynucleotide according to claim 4, wherein the polynucleotide is selected from a group consisting of sequences represented by SEQ. ID. NO: 35-NO:
 37. 6. An expression vector containing the polynucleotide of claim
 4. 7. A transformant prepared by inserting the expression vector of claim 6 into a host cell.
 8. The transformant according to claim 7, wherein the host cell is selected from a group consisting of E. coli, yeast, animal cell lines CHO, Cos-7, NIH3T3 and insect cells.
 9. A recombinant acetylcholine receptor polypeptide with the fusion of two or more T cell epitopes selected from a group consisting of sequences represented by SEQ. ID. NO: 38-NO:
 50. 10. The recombinant acetylcholine receptor polypeptide according to claim 9, wherein the recombinant acetylcholine receptor polypeptide is characterized by being fused with T cell epitopes represented by SEQ. ID. NO: 38-NO:
 50. 11. The recombinant acetylcholine receptor polypeptide according to claim 9, wherein the recombinant acetylcholine receptor polypeptide is characterized by being fused with T cell epitopes represented by SEQ. ID. NO: 44-NO:
 50. 12. The recombinant acetylcholine receptor polypeptide according to claim 10, wherein the T cell epitopes are randomly arranged for the fusion.
 13. The recombinant acetylcholine receptor polypeptide according to claim 11, wherein the T cell epitopes are randomly arranged for the fusion.
 14. A polynucleotide encoding the recombinant acetylcholine receptor polypeptide of claim
 9. 15. The polynucleotide according to claim 14, wherein the polynucleotide is characterized by encoding the recombinant acetylcholine receptor polypeptide with the fusion of every T cell epitope represented by SEQ. ID. NO: 38-NO:
 50. 16. The polynucleotide according to claim 14, wherein the gene is characterized by encoding the recombinant acetylcholine receptor polypeptide with the fusion of every T cell epitope represented by SEQ. ID. NO: 44-NO:
 50. 17. An expression vector containing the polynucleotide of claim
 14. 18. A transformant prepared by inserting the expression vector of claim 17 into a host cell.
 19. The transformant according to claim 18, wherein the host cell is selected from a group consisting of E. coli, yeast, animal cell lines CHO, Cos-7, NIH3T3 and insect cells.
 20. A therapeutic agent for myasthenia gravis containing the polypeptides of claim 1 as an effective ingredient.
 21. A therapeutic agent for myasthenia gravis containing the polypeptides of claim 9 as an effective ingredient.
 22. A therapeutic agent for myasthenia gravis containing the recombinant acetylcholine receptor polypeptide with the deletion of B cell epitope selected from a group consisting of sequences represented by SEQ. ID. NO: 32-NO: 34 and two or more recombinant acetylcholine receptor polypeptides with the fusion of T cell epitopes selected from a group consisting of sequences represented by SEQ. ID. NO: 38-NO:
 50. 23. The therapeutic agent according to claim 22, wherein the agent additionally contains a polypeptide having the amino acid sequence represented by SEQ. ID. NO:
 55. 24. A method for the treatment of myasthenia gravis containing the step of administrating an effective dose of a recombinant polypeptide of acetylcholine receptor a subunit with the deletion of B cell epitope and/or a recombinant polypeptide with the fusion of T cell epitope to mammalian.
 25. The method for the treatment of myasthenia gravis according to claim 24, wherein the recombinant polypeptide is selected from a group consisting of 1) polypeptides represented by SEQ. ID. NO: 32-NO: 34; 2) polypeptides represented by SEQ. ID. NO: 51-NO: 53; and 3) polypeptide represented by SEQ. ID. NO:
 55. 